ENERGY MINIMIZATION USING THE CLASSICAL DENSITY DISTRIBUTION - APPLICATION TO SODIUM-CHLORIDE CLUSTERS

The adiabatic Gaussian density annealing (AGDA) optimization algorithm , based on direct integration of the classical Bloch equation is recip rocal temperature, is employed to study the structures of (NaCl)(n) an d (NaClNa+ clusters. The results of the energy minimizations are compa red with simulated annealing, using molecular dynamics. We model these clusters with a rigid core potential used in previous studies. Overal l, the AGDA algorithm was successful in isolating the lowest-energy mi nima. In contrast to the conclusion of a previous study, we find that molecular-dynamics-based simulated annealing can be quite effective at isolating low-energy minima. However, the effectiveness of the method is strongly dependent on the integration algorithm employed. The hexa gonal and cubic growth forms are found to be most stable for small clu sters and the fee structure is most stable for large clusters in agree ment with previous studies. The difficulty in locating the global ener gy minimum is explained in terms of the statistical properties of the energy landscape.